1. Field of the Invention
The present invention relates to an actuator employing a piezoelectric element in, for example, a head moving actuator employed in a magnetic disk drive.
2. Description of the Related Art
Along with the trend toward more compact and precision information equipment or sensors, there is an increasing demand for an actuator for inching a member. In particular, the demand for an actuator formed by utilizing a piezoelectric element has increased. The piezoelectric actuator is applied to various fields, that is, is applied to a unit for controlling the focus of an optical system, a printing mechanism included in a printer, a unit for driving a probe included in a sensor, or a mechanism for moving a head included in an optical disk drive or a magnetic disk drive (refer to Japanese Unexamined Patent Application Publications Nos. 9-73746 and 5-18741).
By taking a magnetic disk drive for instance, a conventional piezoelectric actuator and its drawbacks will be described below. In the magnetic disk drive, the number of data tracks per unit length (tracks per inch (TPI)) is increased in order to raise a recording density, that is, the width of each track is made narrow in order to improve the recording density offered by the magnetic disk drive. In this case, data must be accurately read or written from or in a narrow track. For this purpose, the precision in positioning a head must be further improved. The piezoelectric actuator is adopted for this purpose.
Specifically, a head moving mechanism has a head suspension, which includes a slider having a magnetic head, fixed to a carriage arm, and the carriage arm is turned in order to move a head. A micro-actuator formed by utilizing a piezoelectric element is adopted for the head moving mechanism in order to slightly move the head suspension or slider, or the head element itself. The present inventor et al. have proposed a shear piezoelectric actuator that utilizes a shear strain in a piezoelectric element (Japanese Unexamined Patent Application Publication Nos. 11-31368 and 2001-43641).
Furthermore, the present inventor et al. have proposed a micro-actuator that has the wiring thereof, which is required for applying a voltage to a piezoelectric element, achieved according to the wire bonding method and that is thin and compact, includes a decreased number of parts, and is thus low in cost (Japanese Unexamined Patent Application Publication No. 2003-61371).
However, when the wire bonding is adapted to directly attach a wire to a piezoelectric element, it poses a problem. Namely, the thickness of the Au electrode film, with which the piezoelectric element is coated, must be equal to or larger than a certain value. Moreover, a stress is applied locally to the piezoelectric element during wire bonding. Furthermore, the electrode side of the piezoelectric element is exposed for the wire bonding.